Elastic moduli ($C_{ij}$) of single-crystal stishovite and post-stishovite are determined using Brillouin light scattering, impulsive stimulated light scattering, and x-ray diffraction up to 70 GPa. The $C_{12}$ of stishovite converges with the $C_{11}$ at $\sim 55\mathrm{GPa}$, where the transverse wave $V_{S1}$ propagating along [110] also vanishes. Landau modeling of the $C_{ij}$, $B_{1g}$ optic mode, and lattice parameters reveals a pseudoproper type ferroelastic post-stishovite transition. The transition would cause peculiar anomalies in $V_S$ and Poisson’s ratio in silica-bearing subducting slabs in the mid-lower mantle.

中文翻译：

---

高压下从斜辉石到后斜辉石的伪适当的铁弹性转变的弹性

弹性模量$C_{\mathrm{一世}Ĵ}$使用布里渊光散射，脉冲激发光散射和高达70 GPa的X射线衍射确定单晶的辉石和辉石后晶。的$C_{12}$ 的辉石与 $C_{11}$ 在 $〜55\mathrm{GPa}$，其中横波 $V_{\mathrm{小号}\mathrm{1个}}$沿着[110]传播也消失了。Landau的建模$C_{\mathrm{一世}Ĵ}$， ${乙}_{\mathrm{1个}G}$光学模式和晶格参数揭示了伪适当类型的铁弹性后stishovite过渡。过渡会导致特殊的异常$V_{\mathrm{小号}}$ 下地幔中含二氧化硅俯冲板中的泊松比。